In the northern parts of the time zone, during the second Sunday in March, at 2:00 a.m. EST, clocks are advanced to 3:00 a.m. EDT leaving a one-hour "gap". During the first Sunday in November, at 2:00 a.m. EDT, clocks are moved back to 1:00 a.m. EST, thus "duplicating" one hour. Southern parts of the zone (Panama and the Caribbean) do not observe daylight saving time.

Contents

History

The Uniform Time Act of 1966 ruled that daylight saving time would run from the last Sunday of April until the last Sunday in October in the United States.[1] The act was amended to make the first Sunday in April the beginning of daylight saving time as of 1987.[1] The Energy Policy Act of 2005 extended daylight saving time in the United States beginning in 2007. So local times change at 2:00 a.m. EST to 3:00 a.m. EDT on the second Sunday in March and return at 2:00 a.m. EDT to 1:00 a.m. EST on the first Sunday in November.[1] In Canada, the time changes as it does in the United States.[2][3]

Until 2006, the portions of Indiana within the Eastern Time Zone observed Eastern Standard Time year-round – except that five counties near Cincinnati and Louisville customarily observed Eastern Daylight Time despite legally being on Eastern Standard Time. See Time in Indiana.

Michigan: All of Michigan observes Eastern Time except for the four counties in the Upper Peninsula along the border with Wisconsin, which observe Central Time – Gogebic, Iron, Dickinson, and Menominee. Historically the entire state observed Central Time. When daylight saving time was first introduced, the Lower Peninsula remained on DST after it formally ended, effectively re-aligning itself into the Eastern Time Zone. The Upper Peninsula continued to observe Central Time until 1972, when all but the four counties noted changed to Eastern Time. Ontonagon is the westernmost county in the Upper Peninsula to entirely observe Eastern Time at a longitude of 89.5°W.

Tennessee: Most of the eastern third of Tennessee is legally on Eastern Time. The area is roughly but not entirely coextensive with the region formally known as "East Tennessee". Specifically, three East Tennessee counties--Bledsoe, Cumberland, and Marion—are on Central Time.

Eastern Time is also used somewhat as a de facto official time for all of the United States, since it includes the capital (Washington, D.C.) and the largest city (New York City). National media organizations will often report when events happened or are scheduled to happen in Eastern Time even if they occurred in another time zone, and TV schedules are also almost always posted in Eastern Time. In the United States, all nationally televised morning programs (except Good Morning America Weekend Edition which some ABC affiliates on the east coast air on a tape-delay), some daytime talk shows, evening newscasts, most talent & awards shows, and any other nationally televised event that airs live on American television during prime time & on the weekends (such as sports television) are broadcast live in the Eastern Time Zone. Major professional sports leagues also post all game times in Eastern time, even if both teams are from the same time zone, outside of Eastern Time. For example, a game time between two teams from Pacific Time Zone will still be posted in Eastern time (for example, one may see "Seattle at Los Angeles" with "10:00 p.m." posted as the start time for the game, often without even clarifying the time is posted in Eastern time).[citation needed]

Most cable television and national broadcast networks advertise airing times in Eastern time. National broadcast networks (ABC, CBS, The CW, Fox Network, NBC) generally have two primary feeds, an eastern feed for Eastern and Central time zones, and a tape-delayed western feed for the Pacific Time Zone. The prime time is set on Eastern and Pacific at 8:00 p.m., with the Central time zone stations receiving the eastern feed at 7:00 p.m. local time. Mountain Time Zone stations receive a separate feed at 7:00 p.m. local time.[citation needed] As Arizona does not observe daylight saving time, during the summer months, it has its own feed at 7:00 p.m. local time.[citation needed] Cable channels with a separate western feed (such as HBO, whose western feed is called "HBOW") generally air the same programming as the eastern feed delayed by three hours. Other cable networks such as the Discovery family of networks repeat their prime time programming three hours later; this allows for the same show to be advertised as airing at "8:00 p.m. E/P" (that is, "8:00 p.m. Eastern and Pacific time"). Networks specializing in the airing of sports events, such as ESPN, advertise all of their programming in Eastern and Pacific, incorporating the 3-hour time difference (as in "8:00 p.m. Eastern/5:00 p.m. Pacific") and leaving viewers in the remaining time zones to calculate start time in their own areas.[citation needed]

Mexico

Quintana Roo: this eastern state followed EST for an almost-17-year period (1982 to some time in 1998).[6] After more than two years of lobbying by a coalition of local hotel owners with the backing of the state's government, the Federal government approved the change to Quintana Roo's time zone, moving it from Central Standard Time (CST) to Eastern Standard Time (EST).[7] The time change took effect on February 1, 2015.[7]

Caribbean Islands

The Bahamas, Cayman Islands and Haiti officially observe both Eastern Standard Time during the winter months and Eastern Daylight Time during the summer months. Cuba is usually the same, with Eastern Standard Time in the winter, and Eastern Daylight Time in the summer, but it often changes on different days. The Turks and Caicos Islands used to follow eastern time with daylight saving but switched in 2015 to the Atlantic Time Zone.

↑The specification for the Eastern Time Zone is set forth at 49 CFR 71.4, and is listed in Text and pdf formats. The boundary between Eastern and Central is set forth at 49 CFR 71.5, and is listed in text and pdf formats.